Telecommunications – Receiver or analog modulated signal frequency converter – Frequency conversion between signal source and receiver
Reexamination Certificate
1999-07-20
2002-05-28
Hunter, Daniel (Department: 2684)
Telecommunications
Receiver or analog modulated signal frequency converter
Frequency conversion between signal source and receiver
C375S316000, C455S263000, C455S307000
Reexamination Certificate
active
06397048
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a communication apparatus which performs frequency conversion processing and to a signal processing apparatus advantageously used for the frequency conversion processing of the communication apparatus.
2. Description of the Related Art
Conventional receivers for high frequency radio multiplex communication or high frequency wired multiplex communication are provided with circuits for performing frequency conversion. Examples of such receivers are a portable telephone terminal, an automobile telephone terminal, a transceiver, a television broadcasting receiver, a radio broadcasting receiver, a cable television (CATV) receiver and the like.
FIG. 16
is a block diagram illustrating an electrical configuration of an FM (Frequency Modulation) radio receiver
1
according to a prior art. The FM radio receiver
1
uses a plurality of channels within a predetermined frequency band, and is utilized in a radio communication network which transmits carrier waves frequency-modulated by base band signals to a plurality of FM radio receivers, respectively, in parallel. The FM radio receiver
1
is, for example, used as a receiver unit of a portable telephone terminal in an analogue portable telephone network.
The FM radio receiver
1
is of a double-super-heterodyne system including an antenna
3
, a high-frequency filter
4
, a low noise amplifier
5
, a first and a second frequency converting units
6
,
7
, an oscillation source
8
, a first and a second intermediate frequency filters
9
,
10
, an amplifier-limiter
11
, an FM demodulation unit
12
, a base band voice processing unit
13
, a speaker
14
and a control unit
15
. The first and the second frequency converting units
6
,
7
include first and second mixers
16
,
18
and first and second local frequency oscillators
17
,
19
, respectively.
The antenna
3
receives an electromagnetic wave and outputs a receive signal corresponding to the received electromagnetic wave. After signal components outside the predetermined frequency band are removed by the high frequency filter
4
, the receive signal is amplified by the low noise amplifier (LNA)
5
, and then supplied to the first mixer
16
. The first local frequency oscillator
17
, using a reference oscillation signal having a predetermined reference frequency oscillated by the oscillation source
8
, generates a first local oscillation signal having a frequency defined based on a designated frequency designated by an operator of the FM radio receiver
1
or a predetermined designated frequency, and the frequency of the receive signal to supply it to the first mixer
16
.
The first mixer
16
mixes the first local oscillation signal and the receive signal to generate a first intermediate frequency signal having a predetermined first intermediate frequency. The first intermediate frequency filter
9
performs filtering of passing only components within a frequency band of a predetermined band width including the designated frequency from the first intermediate frequency signal for channel selection. After being filtered, the first intermediate frequency signal is supplied to the second mixer
18
.
The second local frequency oscillator
19
, using the reference oscillation signal, generates and outputs a second local oscillation signal based on the frequency of the intermediate frequency signal after filtering and a second intermediate frequency. The second mixer
18
mixes the second local oscillation signal and the first intermediate frequency signal after filtering, and generates a second intermediate frequency signal having a predetermined second intermediate frequency. The second intermediate frequency filter
10
performs filtering for passing only components of the channel including the designated frequency from the second intermediate frequency signal for channel selection. The second intermediate frequency signal after filtering is supplied to amplifier-limiter
11
.
The amplifier-limiter
11
amplifies the second intermediate frequency signal after filtering, and limits the amplitude of the second intermediate signal after amplification so as to remove amplitude modulation (AM: amplitude modulation) components. The FM demodulation unit
12
, to reconstruct the base band signal, performs frequency discrimination on the second intermediate frequency signal after amplitude limitation. The base band voice processing unit
13
performs a processing defined in the radio communication network on the resultant signal of the frequency discrimination, and supply the signal to the speaker
14
or the control unit
15
. The speaker
14
electroacoustically converts the signal after the processing to output the resultant sound. In the case where the signal after the processing represents protocol control data or user data, the control unit
15
, based on the data, performs processing relating to the control of the entire FM radio receiver
1
. The above describes the FM radio receiver
1
.
In the FM radio receiver
1
, the high frequency filter
4
and the first and the second intermediate frequency filters
9
,
10
are generally formed of a dielectric material or ceramic material, and the low noise amplifier
5
, the amplifier-limiter
11
, the FM demodulation unit
12
, the base band voice processing unit
13
and the first and the second mixers
16
,
18
are implemented by semiconductor elements. Therefore, it is difficult to integrate the high frequency filter
4
and the first and the second intermediate frequency filters
9
,
10
with the low noise amplifier
5
, the amplifier-limiter
11
, the FM demodulation unit
12
, the base band voice processing unit
13
and the first and the second mixers
16
,
18
into one integrated circuit.
Recently, radio communications utilizing a higher frequency band such as a G (giga) Hz band than that of the conventional radio communications have been proposed. To apply a communication apparatus with the same configuration as the FM radio receiver
1
for the radio communication using GHz band, each component of the communication apparatus is required to operate at a higher operating frequency than that of the conventional FM radio receivers. Generally, in the case where each of the filters
4
,
9
,
10
is implemented by a semiconductor circuit, that is, each of the filters
4
,
9
,
10
is implemented by a so-called digital filter, when the filters
4
,
9
,
10
are operated at the operating frequency proper to the radio communication using the GHz band, there is often the case that characteristics required for the radio communication is not obtained. This is because, the upper limit operating frequency of the semiconductor circuit is determined due to the configuration and the characteristics of the circuit itself, and if the circuit is operated at a frequency higher than the upper limit operating frequency, the operation will become unstable.
Japanese Unexamined Patent Publication JP-A 9-135149 (1997) discloses that, in a digital filter which performs digital filtering for processing digital coded signals, a technology to reduce the operating frequency of components within the digital filter. The digital filter includes one input portion, one switch, a plurality of FIFO type memories and a plurality of multipliers. A plurality of sets of objective data to be processed are acquired by sampling a signal to be inputted at an input sampling frequency Fe.
The objective data to be processed arrives at the input portion sequentially with the input sampling frequency Fe. The switch is interposed between the input portion and each of the memories, and in response to the arrival of the data, distributes the plurality of sets of data into the plurality of memories to be stored therein. Each of the multipliers operates according to a clock signal of a clock frequency which is L/M times the input sampling frequency Fe, and determines each of the product of the data memorized in each of the memories and one of plurality of predetermined coefficients. The ab
Corsaro Nick
Hunter Daniel
Nixon & Vanderhye P.C.
Sharp Kabushiki Kaisha
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